1. Field of the Invention
The invention relates generally to a universal milling and drilling machine, and more particularly to a machine with a swivel milling head with automatic reset from horizontal to vertical machining, and a shift transmission enabling high torque at low rotation speed.
2. Discussion of the Related Art
In such a machine tool, known, for example, from German patent 2,944,983, a horizontal work spindle is arranged in the lower part of a spindle housing, which is used to carry out horizontal operations on a clamped workpiece in the conventional way. At the front wall of the spindle housing, being inclined upward by 45.degree., a swivel head is mounted which is rotatable about its 45.degree. center axis. On one side of this swivel head, a vertical milling head is fixed, which can, by a 180.degree. turning movement of the swivel head in the inclined plane, be moved from an upper horizontal standby position to its vertical operation position, and which can be fixed in this position. In the rear part of the spindle housing, a shift transmission coupled with a driving motor is arranged, the driving shaft of which is coupled, via a main shaft extending through the spindle housing and a sliding gear arrangement, either to the horizontal work spindle or, via an additional intermediate shaft with a bevel gear transmission, to the vertical work spindle. As the shift transmission is already arranged at the start of the whole gear train, all driving shafts, gears and related bearings located between the shift gear and the vertical and horizontal spindle must be designed and dimensioned for the transmission of high torques. Furthermore, the complete horizontal spindle arrangement demands considerable structural complexities and relatively large dimensions.
Further, a spindle arrangement for a universal milling and drilling machine is known (SHW-Prospekt UF5), in which a swivel head is mounted on the free front surface of the spindle head, the swivel head being arranged in a upwardly extending plane incline by 45.degree. and rotatable by 180.degree. with respect to the spindle head, respectively. This swivel head carries the horizontal spindle on one front surface, and a vertical milling head is screwed to the other front surface in the conventional way. By turning the swivel head about a rotation axis extending perpendicular to the plane inclined by 45.degree., either the horizontal spindle or the vertical spindle can be moved to its operation position. After the positioning of the one or the other work spindle, the positive or non-positive connection to the driving shaft of the main transmission is effected.